Microsoft ASP.NET Core: Security feature bypass via improper input validation
Summary
An improper input validation flaw in ASP.NET Core allows an unauthenticated remote attacker to bypass a security feature of the application. The attack has high complexity and requires no privileges or user interaction. Microsoft rates the issue Important (CVSS 6.5) and affects only the .NET 11 line; which security feature can be bypassed is unknown.
Affected
- Microsoft .NET 11.0 runtime packages (Linux, macOS, Windows) from 11.0.0-preview.1 up to, but not including, 11.0.0
- Microsoft Visual Studio 2026 version 18.12: unverified, the version ranges in the sources are malformed
- .NET 8, 9 and 10 are not listed as affected
Fixed in
- Upgrade .NET 11 runtime packages to 11.0.0
Workaround
Unknown.
Exploitation
- No public disclosure or known exploitation
- CISA SSVC: exploitation none, not automatable, partial technical impact
Our recommendation
- Identify all .NET 11 preview, RC and GA runtimes and applications, including self-contained and Visual Studio-built deployments
- Update affected runtime packages to 11.0.0 with the normal patch cycle, and restart applications; recompile and redeploy self-contained applications
- Prioritise internet-facing .NET 11 web applications
- No action needed for SMEs running only .NET 8, 9 or 10 with respect to this CVE
Information from Microsoft (Patch Tuesday November 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-114156 msrc.microsoft.com
- dotnet/announcements issue 510: affected runtime packages and fix github.com
- .NET November 2026 servicing updates devblogs.microsoft.com
- dotnet/announcements issue 504: ASP.NET Core November 2026 announcement github.com
- Rapid7: Patch Tuesday November 2026 www.rapid7.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 11 Nov 2026, 12:18.
Original description (NVD)
Improper input validation in ASP.NET Core allows an unauthorized attacker to bypass a security feature over a network.
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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